The invention relates to a ground fault detector and, more particularly, relates to a ground fault detector for use on tanker trucks.
The transfer of flammable liquids through non-electrical conducting hose from and to tanker trucks has resulted in serious explosions. It is believed that a charge of static electricity generated during the transfer operation creates a hot spark which ignites the flammable gases emitted by the said liquid. It is well known to electrically ground the tanker truck, the tank and related equipment receiving or providing the flammable liquid. However, a faulty ground such as an incomplete ground due to failure in electrical continuity may remain undetected resulting in creation of the danger of an explosion.
U.S. Pat. No. 3,290,668 discloses a grounding and indicating device operating from an AC power supply with a transformer to supply a weak current to a grounding circuit. Closing of the grounding circuit energizes a lamp--photoconductive cell combination which triggers a series of relays for actuating control and warning circuits. This device requires an AC power supply, which often is not available or convenient, poses a risk of sparking due to the presence of the high voltage AC circuitry, and is expensive due to its complexity.
It is an object of the present invention to provide a small and portable ground fault detector for use with tanker trucks transferring flammable liquids. It is desired that the ground fault detector be provided with audio and visual modes for reliable identification of the lack or presence of electrical grounding and for the instantaneous detection of a change in conditions during transfer.